There are two distinct ways of setting off an explosive charge. The first uses a fuse which burns along its length until the combustion region reaches the explosive and causes detonation of the explosive, either directly or via an intermediate detonator. The second method of setting off an explosive uses detonating cord. Such a cord does not burn, but rather is the subject of continuous detonation along its length.
Considerable research has been put into improving the properties of detonating cords and, for example, British Patents Nos. 1582903 and 1582904 to E I Du Pont de Nemours & Co. are concerned with continuously extruding a core of plasticised explosive and with sheathing that core to protect the core and to prevent necking or kinking of the detonating cord.
Research into fuses, on the other hand, has been neglected and the most commonly used fuse still comprises gun powder in a paper wrapping within a woven outer tube. Such a fuse presents operating difficulties since the powdered gunpowder may not continuously fill the fuse thereby forming a break or "holiday" in the fuse which will of course interrupt the burning and prevent the fuse from achieving its function.